A flame retardant polyurethane adhesive for reflective heat stickers

Abstract

The present invention relates to the technical field of adhesives and discloses a flame-retardant polyurethane adhesive for reflective heat-resistant stickers. The adhesive comprises organophosphorus-modified polyethylene glycol, phthalazine-modified epoxy-terminated silicone oil, isophorone diisocyanate, a catalyst, a chain extender, triethylamine, distilled water, a stabilizer, and a filler. The organophosphorus-modified polyethylene glycol is prepared by introducing an organophosphorus flame retardant into the molecular chain of polyethylene glycol diglycidyl ether. The phthalazine-modified epoxy-terminated silicone oil is prepared by introducing a rigid phthalazine structure into the epoxy-terminated silicone oil structure, and the phthalazine-modified epoxy-terminated silicone oil participates in the synthesis process of the polyurethane as a soft segment of the polyurethane, thereby effectively improving the high-temperature resistance of the polyurethane adhesive. Moreover, since the structure contains the flame-retardant elements nitrogen and silicon, the adhesive can produce a synergistic flame-retardant effect with the organophosphorus flame retardant, thereby further enhancing the flame-retardant performance of the polyurethane adhesive.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and in particular to a flame retardant polyurethane adhesive for reflective heat stickers. Background Art

[0002] Reflective materials, also known as retroreflective materials, play an important role in warning and safety protection in daily life due to their ability to reflect light backwards. Reflective materials are widely used in transportation, firefighting, railways, water transport, mining, and other fields. Commonly used materials include reflective cloth, reflective marking paint, reflective leather, and reflective heat stickers. Heat stickers are commonly used in uniforms for sanitation workers, construction workers, firefighters, and traffic police. In addition to the high-refractive index glass beads that provide retroreflective effects, the adhesive that bonds the material to the clothing also plays a crucial role. Adhesives can be categorized by chemical composition into epoxy resin adhesives, polyurethane adhesives, and polyvinyl acetate adhesives. Polyurethane adhesives are a highly versatile adhesive. Their molecular chains contain highly polar and chemically active isocyanate and urethane groups, resulting in excellent chemical adhesion to a variety of materials and excellent flexibility, oil resistance, abrasion resistance, and corrosion resistance.

[0003] Chinese patent application number CN202010379162.6 discloses a polyurethane adhesive composition and a polyurethane adhesive. The prepared polyurethane adhesive can form a high initial strength in a relatively short period of time without heating, and has sufficient mechanical strength and bonding stability. Chinese patent application number CN202210640545.3 discloses a reactive polyurethane adhesive for bonding and a preparation method thereof. The prepared polyurethane adhesive has good initial adhesion, moderate operating temperature, easy coating, no foaming, and fast curing speed. It can be widely used in the bonding of substrates such as solid wood, composite panels, and fiberboards of different densities with decorative layers. However, for firefighters who often go in and out of fire scenes, the reflective heat stickers on their fire suits must not only meet the reflective requirements, but also have flame retardant and high temperature resistance to avoid the reflective heat stickers falling off and losing their reflective effect due to reduced bonding strength. This places higher requirements on the polyurethane adhesive used for reflective heat stickers. However, existing polyurethane adhesives have poor heat resistance and are easily hydrolyzed under high temperature conditions after curing, reducing the bonding strength. At the same time, polyurethane adhesives are flammable and will burn and produce large amounts of toxic smoke when exposed to fire. Therefore, the development of a polyurethane adhesive with flame retardant and high temperature resistant properties is of great significance to the development of adhesives. Summary of the Invention

[0004] The purpose of the present invention is to provide a flame retardant polyurethane adhesive for reflective heat patches, which solves the following technical problems:

[0005] (1) Solved the problem of poor flame retardancy of polyurethane adhesives;

[0006] (2) Solved the problem of poor high temperature resistance of polyurethane adhesives.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] A flame-retardant polyurethane adhesive for reflective heat transfer stickers comprises the following raw materials in parts by weight: 50-60 parts of organophosphorus-modified polyethylene glycol, 5-15 parts of phthalazine-modified epoxy-terminated silicone oil, 30-40 parts of isophorone diisocyanate, 1-2 parts of a catalyst, 1-5 parts of a chain extender, 10-12 parts of triethylamine, 30-40 parts of distilled water, 0.1-0.2 parts of a stabilizer, and 5-10 parts of a filler. The organophosphorus-modified polyethylene glycol is prepared by introducing an organophosphorus flame retardant into a polyethylene glycol diglycidyl ether structure; the phthalazine-modified epoxy-terminated silicone oil is prepared by introducing a phthalazine rigid structure into the epoxy-terminated silicone oil structure.

[0009] Furthermore, the catalyst is any one of dibutyltin dilaurate or zinc isooctanoate.

[0010] Furthermore, the chain extender is any one of 1,4-butanediol, 1,6-hexanediol or 1,3-propylene glycol; the stabilizer is any one of salicylic acid, oxalic acid, nitric acid, benzoic acid or phosphoric acid; and the filler is any one of talc, light calcium carbonate or titanium dioxide.

[0011] Furthermore, the preparation method of the organophosphorus-modified polyethylene glycol is specifically as follows:

[0012] Add polyethylene glycol diglycidyl ether to N,N-dimethylformamide, then add a catalyst, stir evenly, increase the temperature to 130-140°C, then add dibenzyl phosphate, react for 3-4 hours, and after the reaction is completed, remove the solvent by reduced pressure distillation to obtain organophosphorus-modified polyethylene glycol.

[0013] Furthermore, the catalyst is triphenylphosphine.

[0014] Through the above technical solution, under the action of a catalyst and high temperature, the epoxy groups in the polyethylene glycol diglycidyl ether structure react with the hydroxyl groups in the dibenzyl phosphate structure, thereby introducing an organophosphorus flame retardant at both ends of the polyethylene glycol diglycidyl ether molecular chain. At the same time, active hydroxyl groups are introduced due to the ring-opening reaction, thereby preparing an organophosphorus-modified polyethylene glycol.

[0015] Furthermore, the preparation method of the phthalazine-modified epoxy-terminated silicone oil is specifically as follows:

[0016] Add the epoxy-terminated silicone oil to xylene, stir evenly, raise the temperature to 60-70°C, then add 4-(4-hydroxyphenyl)phthalazin-1-ol, and react for 4-6 hours. After the reaction is completed, remove the solvent by reduced pressure distillation to obtain phthalazine-modified epoxy-terminated silicone oil.

[0017] Through the above technical solution, the imino group contained in the 4-(4-hydroxyphenyl)phthalazin-1-ol structure and the epoxy group in the terminal epoxy silicone oil structure undergo a ring-opening addition reaction, thereby introducing the rigid structure of phthalazine into the structure of the silicone oil and simultaneously introducing multiple active hydroxyl groups to prepare phthalazine-modified terminal epoxy silicone oil.

[0018] Furthermore, the preparation method of the polyurethane adhesive comprises the following steps:

[0019] Step 1: Mix the organophosphorus-modified polyethylene glycol, phthalazine-modified epoxy-terminated silicone oil, isophorone diisocyanate and catalyst, stir evenly, raise the temperature to 60-70°C, and react for 2-3 hours to obtain a modified polyurethane prepolymer;

[0020] Step 2: Add a chain extender to the modified polyurethane prepolymer, continue the reaction for 3-5 hours, reduce the temperature to 30-40°C, add triethylamine for neutralization for 6-8 minutes, then add distilled water, stir and emulsify for 20-30 minutes to obtain a modified polyurethane emulsion;

[0021] Step 3: Pour the modified polyurethane emulsion, stabilizer and filler into a mixer, stir evenly, and discharge the mixture to obtain a polyurethane adhesive.

[0022] Furthermore, in step three, the stirring speed of the mixer is 800-1000 r / min, and the stirring time is 30-40 min.

[0023] Beneficial effects of the present invention:

[0024] (1) The present invention introduces active hydroxyl groups into the molecular chain of polyethylene glycol diglycidyl ether to participate in the synthesis process of the polyurethane adhesive, and introduces an organophosphorus flame retardant into the polyurethane molecular chain. The organophosphorus flame retardant can generate phosphoric acid derivatives when burned. The catalytic carbonization effect of the phosphoric acid derivatives can form a carbon layer on the surface of the polyurethane adhesive, covering its surface, isolating oxygen and heat, and preventing the polyurethane adhesive from continuing to burn, thereby enhancing the flame retardant properties of the polyurethane adhesive. In addition, the polyethylene glycol diglycidyl ether molecular chain contains polar group ether bonds, which can generate hydrogen bonds with the adhered substrate, helping to improve the adhesion of the polyurethane adhesive and enhance the bonding strength of the polyurethane adhesive.

[0025] (2) The present invention regulates the structure of the polyurethane molecular chain by preparing phthalazine-modified end-epoxy silicone oil. On the one hand, the silicone oil molecular chain contains a large number of Si-O bonds, which have a high bond energy and can withstand higher temperatures. It can synergize with the rigid structure of phthalazine to improve the high-temperature resistance of the polyurethane adhesive. On the other hand, the introduced phthalazine-modified end-epoxy silicone oil structure contains flame retardant elements nitrogen and silicon, which produce a synergistic flame retardant effect with the organic phosphorus flame retardant, further improving the flame retardant performance of the polyurethane adhesive. In addition, the multiple hydroxyl groups in the phthalazine-modified end-epoxy silicone oil structure can produce a cross-linking effect during the polyurethane synthesis process to form a polyurethane molecular chain structure with a three-dimensional cross-linked network, thereby improving the cohesion of the polyurethane adhesive and further improving the bonding strength and high-temperature resistance of the polyurethane adhesive.

[0026] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 IR spectra of epoxy-terminated silicone oil and phthalazine-modified epoxy-terminated silicone oil in Example 1 of the present invention. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] Example 1

[0031] 1. Preparation of organophosphorus-modified polyethylene glycol

[0032] 5 g of polyethylene glycol diglycidyl ether was added to 50 mL of N,N-dimethylformamide, and then 0.1 g of triphenylphosphine was added. The mixture was stirred evenly, and the temperature was raised to 140°C. Then, 2.8 g of dibenzyl phosphate was added and the mixture was reacted for 3 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain organophosphorus-modified polyethylene glycol.

[0033] Weigh 0.1g of organophosphorus-modified polyethylene glycol and place it in a digestion bottle. Add 5mL of concentrated nitric acid and 5mL of concentrated sulfuric acid, boil for 30 minutes, cool, and then transfer to a 250mL volumetric flask to the volume. Measure 50mL of the fixed volume solution into a 250mL beaker, add 50mL of water, cover with a watch glass, and heat on an electric stove until boiling. Remove the beaker and add 50mL of quinoline molybdate solution while it is hot, and heat again to a slight boil. Remove the beaker and cool to room temperature, and then filter through a glass frit funnel that has been dried to constant weight in an electric constant temperature drying oven at 180℃. Place the funnel and precipitate in a 180℃ oven to constant weight for about 3 hours, weigh, and perform a blank experiment at the same time. Calculate the phosphorus content ω in the organophosphorus-modified polyethylene glycol using the formula:

[0034]

[0035] Wherein m1 is the mass of quinoline phosphomolybdate precipitate generated in the organophosphorus-modified polyethylene glycol solution, g; m0 is the mass of quinoline phosphomolybdate precipitate generated in the blank experiment solution, g; m is the mass of the organophosphorus-modified polyethylene glycol, g; 0.07 is the coefficient for converting quinoline phosphomolybdate to phosphorus; after testing, the phosphorus content ω in the organophosphorus-modified polyethylene glycol is 5.28%.

[0036] 2. Preparation of phthalazine-modified epoxy-terminated silicone oil

[0037] 10 g of epoxy-terminated silicone oil was added to 100 mL of xylene, stirred evenly, and the temperature was raised to 70°C. 0.3 g of 4-(4-hydroxyphenyl)phthalazin-1-ol was added and reacted for 4 h. After the reaction was completed, the solvent was removed by distillation under reduced pressure to obtain phthalazine-modified epoxy-terminated silicone oil;

[0038] The infrared characterization of epoxy-terminated silicone oil and phthalazine-modified epoxy-terminated silicone oil is shown in the test results. Figure 1 ,Depend on Figure 1 It can be seen that compared with the epoxy-terminated silicone oil, the phthalazine-modified epoxy-terminated silicone oil has a -1 The absorption peak of hydroxyl group appears at 3000~3100cm -1 The absorption peak of benzene ring appears at 1600~1700cm -1 The stretching vibration absorption peak of C=0 appears at 1263cm -1 The absorption peak of the epoxy group at the end of the epoxy group silicone oil disappears. This is because the epoxy group in the epoxy-terminated silicone oil and the hydroxyl group of 4-(4-hydroxyphenyl)phthalazin-1-ol undergo a ring-opening addition reaction, introducing active hydroxyl groups and introducing the rigid structure of phthalazine into the structure of the epoxy-terminated silicone oil.

[0039] 3. Preparation of polyurethane adhesive

[0040] Step 1: Mix 50 parts of organophosphorus-modified polyethylene glycol, 5 parts of phthalazine-modified epoxy-terminated silicone oil, 30 parts of isophorone diisocyanate, and 1 part of dibutyltin dilaurate, stir evenly, raise the temperature to 60°C, and react for 2 hours to obtain a modified polyurethane prepolymer;

[0041] Step 2: Add 1 part of 1,3-propylene glycol to the modified polyurethane prepolymer, continue the reaction for 3 hours, reduce the temperature to 30°C, add 10 parts of triethylamine to neutralize for 6 minutes, then add 30 parts of distilled water, stir and emulsify for 20 minutes to obtain a modified polyurethane emulsion;

[0042] Step 3: Pour the modified polyurethane emulsion, 0.1 parts of benzoic acid and 5 parts of talc into a mixer, stir at a speed of 800 r / min for 30 minutes, and discharge the material to obtain a polyurethane adhesive.

[0043] Example 2

[0044] Preparation of polyurethane adhesive

[0045] Step 1: 55 parts of organophosphorus-modified polyethylene glycol, 10 parts of phthalazine-modified epoxy-terminated silicone oil, 30 parts of isophorone diisocyanate, and 1.5 parts of dibutyltin dilaurate were mixed, stirred evenly, and the temperature was raised to 65° C. and reacted for 2.5 hours to obtain a modified polyurethane prepolymer;

[0046] Step 2: Add 3 parts of 1,3-propylene glycol to the modified polyurethane prepolymer, continue the reaction for 4 hours, reduce the temperature to 35°C, add 11 parts of triethylamine to neutralize for 7 minutes, then add 35 parts of distilled water, stir and emulsify for 25 minutes to obtain a modified polyurethane emulsion;

[0047] Step 3: Pour the modified polyurethane emulsion, 0.15 parts of benzoic acid and 8 parts of talc into a mixer, stir at a speed of 900 r / min for 35 minutes, and discharge the material to obtain a polyurethane adhesive.

[0048] The preparation methods of the organophosphorus-modified polyethylene glycol and the phthalazine-modified epoxy-terminated silicone oil are the same as those in Example 1.

[0049] Example 3

[0050] Preparation of polyurethane adhesive

[0051] Step 1: Mix 60 parts of organophosphorus-modified polyethylene glycol, 15 parts of phthalazine-modified epoxy-terminated silicone oil, 40 parts of isophorone diisocyanate and 2 parts of dibutyltin dilaurate, stir evenly, raise the temperature to 70°C, and react for 3 hours to obtain a modified polyurethane prepolymer;

[0052] Step 2: Add 5 parts of 1,3-propylene glycol to the modified polyurethane prepolymer, continue the reaction for 5 hours, reduce the temperature to 40°C, add 12 parts of triethylamine to neutralize for 8 minutes, then add 40 parts of distilled water, stir and emulsify for 30 minutes to obtain a modified polyurethane emulsion;

[0053] Step 3: Pour the modified polyurethane emulsion, 0.2 parts of benzoic acid and 10 parts of talc into a mixer, stir at a speed of 1000 r / min for 40 minutes, and discharge the material to obtain a polyurethane adhesive.

[0054] The preparation methods of the organophosphorus-modified polyethylene glycol and the phthalazine-modified epoxy-terminated silicone oil are the same as those in Example 1.

[0055] Comparative Example 1

[0056] Preparation of polyurethane adhesive

[0057] Step 1: 15 parts of phthalazine-modified epoxy-terminated silicone oil, 40 parts of isophorone diisocyanate and 2 parts of dibutyltin dilaurate were mixed, stirred evenly, and the temperature was raised to 70° C. and reacted for 3 hours to obtain a modified polyurethane prepolymer;

[0058] Step 2: Add 5 parts of 1,3-propylene glycol to the modified polyurethane prepolymer, continue the reaction for 5 hours, reduce the temperature to 40°C, add 12 parts of triethylamine to neutralize for 8 minutes, then add 40 parts of distilled water, stir and emulsify for 30 minutes to obtain a modified polyurethane emulsion;

[0059] Step 3: Pour the modified polyurethane emulsion, 0.2 parts of benzoic acid and 10 parts of talc into a mixer, stir at a speed of 1000 r / min for 40 minutes, and discharge the material to obtain a polyurethane adhesive.

[0060] The preparation method of the phthalazine-modified epoxy-terminated silicone oil is the same as that in Example 1.

[0061] Comparative Example 2

[0062] Preparation of polyurethane adhesive

[0063] Step 1: 60 parts of organophosphorus modified polyethylene glycol, 40 parts of isophorone diisocyanate and 2 parts of dibutyltin dilaurate are mixed, stirred evenly, raised to 70°C, and reacted for 3 hours to obtain a modified polyurethane prepolymer;

[0064] Step 2: Add 5 parts of 1,3-propylene glycol to the modified polyurethane prepolymer, continue the reaction for 5 hours, reduce the temperature to 40°C, add 12 parts of triethylamine to neutralize for 8 minutes, then add 40 parts of distilled water, stir and emulsify for 30 minutes to obtain a modified polyurethane emulsion;

[0065] Step 3: Pour the modified polyurethane emulsion, 0.2 parts of benzoic acid and 10 parts of talc into a mixer, stir at a speed of 1000 r / min for 40 minutes, and discharge the material to obtain a polyurethane adhesive.

[0066] The preparation method of the organophosphorus-modified polyethylene glycol is the same as that in Example 1.

[0067] Comparative Example 3

[0068] Preparation of polyurethane adhesive

[0069] Step 1: Mix 60 parts of polyoxypropylene glycol, 15 parts of phthalazine-modified epoxy-terminated silicone oil, 40 parts of isophorone diisocyanate and 2 parts of dibutyltin dilaurate, stir evenly, increase the temperature to 70°C, and react for 3 hours to obtain a modified polyurethane prepolymer;

[0070] Step 2: Add 5 parts of 1,3-propylene glycol to the modified polyurethane prepolymer, continue the reaction for 5 hours, reduce the temperature to 40°C, add 12 parts of triethylamine to neutralize for 8 minutes, then add 40 parts of distilled water, stir and emulsify for 30 minutes to obtain a modified polyurethane emulsion;

[0071] Step 3: Pour the modified polyurethane emulsion, 0.2 parts of benzoic acid and 10 parts of talc into a mixer, stir at a speed of 1000 r / min for 40 minutes, and discharge the material to obtain a polyurethane adhesive.

[0072] The preparation method of the phthalazine-modified epoxy-terminated silicone oil is the same as that in Example 1.

[0073] Comparative Example 4

[0074] Preparation of polyurethane adhesive

[0075] Step 1: Mix 60 parts of polyoxypropylene glycol, 40 parts of isophorone diisocyanate and 2 parts of dibutyltin dilaurate, stir evenly, increase the temperature to 70°C, and react for 3 hours to obtain a polyurethane prepolymer;

[0076] Step 2: Add 5 parts of 1,3-propylene glycol to the polyurethane prepolymer, continue the reaction for 5 hours, reduce the temperature to 40°C, add 12 parts of triethylamine to neutralize for 8 minutes, then add 40 parts of distilled water, stir and emulsify for 30 minutes to obtain a polyurethane emulsion;

[0077] Step 3: Pour the polyurethane emulsion, 0.2 parts of benzoic acid and 10 parts of talc into a mixer, stir at a speed of 1000 r / min for 40 minutes, and discharge the material to obtain a polyurethane adhesive.

[0078] Performance testing

[0079] a. The polyurethane adhesives prepared in Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention were poured into a flat mold and placed in a vacuum oven at 60°C for curing for 5 hours. The molds were then cut into specimens with a size of 80 mm × 10 mm × 4 mm. Combustion performance tests were performed with reference to the national standard GB / T 2406.2-2009. The test results are shown in the table below:

[0080]

[0081] As can be seen from the above table, the polyurethane adhesives prepared in Examples 1 to 3 of the present invention have a high limiting oxygen index and have good flame retardant properties. The polyurethane adhesive prepared in Comparative Example 2 does not introduce phthalazine-modified epoxy-terminated silicone oil containing the flame retardant elements nitrogen and silicon, but introduces an organophosphorus flame retardant, and has relatively good flame retardancy. The polyurethane adhesives prepared in Comparative Examples 1, 3, and 4 do not add an organophosphorus flame retardant, and therefore have poor flame retardancy.

[0082] b. The polyurethane adhesives prepared in Examples 1 to 3 and Comparative Examples 1 to 4 of the present invention were evenly coated between two polyamide plastic plates. After bonding the two polyamide plastic plates, a pressure of 1 MPa was applied to the bonded portion. The peel strength X1 (N / cm) of the bonded composite plate was then measured at room temperature. The composite plates prepared in the same manner were then placed in a heat aging test chamber at 150° C. for 12 hours, and their peel strength X2 (N / cm) was measured. The peel strength reduction rate was calculated using the formula:

[0083]

[0084] The test results are shown in the table below:

[0085]

[0086] As can be seen from the above table, the polyurethane adhesives prepared in Examples 1 to 3 of the present invention have a low rate of reduction in peel strength, indicating that after the polyurethane adhesives are subjected to high-temperature treatment, they still have excellent bonding strength and good high-temperature resistance. The polyurethane adhesives prepared in Comparative Examples 1 and 3 both introduce a rigid phthalazine structure, but do not introduce an organophosphorus-modified polyethylene glycol and do not contain ether bonds that enhance adhesion. Therefore, their bonding strength and high-temperature resistance are average. The polyurethane adhesives prepared in Comparative Examples 2 and 4 have a high rate of reduction in peel strength, poor bonding strength, and poor high-temperature resistance due to the lack of a rigid phthalazine structure.

[0087] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A flame retardant polyurethane adhesive for reflective heat transfer stickers, characterized in that: The polyurethane adhesive comprises the following raw materials in parts by weight: 50-60 parts of organophosphorus-modified polyethylene glycol, 5-15 parts of phthalazine-modified epoxy-terminated silicone oil, 30-40 parts of isophorone diisocyanate, 1-2 parts of a catalyst, 1-5 parts of a chain extender, 10-12 parts of triethylamine, 30-40 parts of distilled water, 0.1-0.2 parts of a stabilizer, and 5-10 parts of a filler. The organophosphorus-modified polyethylene glycol is prepared by introducing an organophosphorus flame retardant into the structure of polyethylene glycol diglycidyl ether; and the phthalazine-modified epoxy-terminated silicone oil is prepared by introducing a phthalazine rigid structure into the structure of the epoxy-terminated silicone oil.

2. The flame retardant polyurethane adhesive for reflective heat transfer stickers according to claim 1, characterized in that: The catalyst is any one of dibutyltin dilaurate or zinc isooctanoate.

3. The flame retardant polyurethane adhesive for reflective heat transfer stickers according to claim 1, characterized in that: The chain extender is any one of 1,4-butanediol, 1,6-hexanediol or 1,3-propylene glycol; the stabilizer is any one of salicylic acid, oxalic acid, nitric acid, benzoic acid or phosphoric acid; and the filler is any one of talc, light calcium carbonate or titanium dioxide.

4. The flame retardant polyurethane adhesive for reflective heat transfer stickers according to claim 1, characterized in that: The preparation method of the organophosphorus-modified polyethylene glycol is specifically as follows: Add polyethylene glycol diglycidyl ether to N,N-dimethylformamide, then add a catalyst, stir evenly, increase the temperature to 130-140°C, then add dibenzyl phosphate, react for 3-4 hours, and after the reaction is completed, remove the solvent by reduced pressure distillation to obtain organophosphorus-modified polyethylene glycol.

5. The flame retardant polyurethane adhesive for reflective heat transfer stickers according to claim 4, characterized in that: The catalyst is triphenylphosphine.

6. The flame retardant polyurethane adhesive for reflective heat transfer stickers according to claim 1, characterized in that: The preparation method of the phthalazine-modified epoxy-terminated silicone oil is specifically as follows: Add the epoxy-terminated silicone oil to xylene, stir evenly, raise the temperature to 60-70°C, then add 4-(4-hydroxyphenyl)phthalazin-1-ol, and react for 4-6 hours. After the reaction is completed, remove the solvent by reduced pressure distillation to obtain phthalazine-modified epoxy-terminated silicone oil.

7. The flame retardant polyurethane adhesive for reflective heat transfer stickers according to claim 1, characterized in that: The preparation method of the polyurethane adhesive comprises the following steps: Step 1: Mix the organophosphorus-modified polyethylene glycol, phthalazine-modified epoxy-terminated silicone oil, isophorone diisocyanate and catalyst, stir evenly, raise the temperature to 60-70°C, and react for 2-3 hours to obtain a modified polyurethane prepolymer; Step 2: Add a chain extender to the modified polyurethane prepolymer, continue the reaction for 3-5 hours, reduce the temperature to 30-40°C, add triethylamine for neutralization for 6-8 minutes, then add distilled water, stir and emulsify for 20-30 minutes to obtain a modified polyurethane emulsion; Step 3: Pour the modified polyurethane emulsion, stabilizer and filler into a mixer, stir evenly, and discharge the mixture to obtain a polyurethane adhesive.

8. The flame retardant polyurethane adhesive for reflective heat transfer stickers according to claim 7, characterized in that: In step 3, the stirring speed of the mixer is 800-1000 r / min, and the stirring time is 30-40 min.

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